Epic tales of the earliest Britons, misguided quests for happiness and the long, long life of a sexless tortoise are among the finalists shortlisted for the Royal Society's prestigious annual science book prize, announced today.

Six books remain in contention for the £10,000 prize, which has previously been claimed by Bill Bryson, Stephen Hawking and the eminent string theorist Brian Greene.

This year, the casualties to fall by the wayside include Matt Ridley's biography of Francis Crick, a history of the universe from Patrick Moore and his rock acquaintance Brian May, and the Sun's Giant Leaps, which depicts groundbreaking scientific achievements as front-page splashes.

The shortlisted authors include Eric Kandel, a Columbia University neuroscientist and Nobel prizewinner, whose memoir, In Search of Memory, charts the scientist's career from childhood in Nazi-occupied Vienna to his wide-ranging investigation of the psyche. The scientist, a world authority on the mechanism of memory, asserts that one day medicine will provide a little red pill to boost the memory of those who are losing it, and a little blue pill for those who strive to forget.

In Homo Britannicus, Chris Stringer, head of human origins at the Natural History Museum in London, describes the human invasion of Britain from the first, tentative steps 700,000 years ago. From that time on, our early ancestors endured extremes of climate and company. They lived alongside hippos and sabre-tooth tigers when the country was basking in tropical heat, and later, when the cold came, shared the land with reindeer and mammoths before being forced to flee.

Two of the books highlight environmental issues: Robert Henson's Rough Guide to Climate Change, and Henry Nicholls's Lonesome George. The latter unravels the history of a conservation icon, a 200lb giant tortoise, aged somewhere between 60 and 200, which was rescued from a remote Galapagos island, threatened by knife-wielding protesters, and has steadfastly refused to produce sperm, despite the efforts of a Swiss graduate student.

In Stumbling on Happiness, Daniel Gilbert, a professor of psychology at Harvard, combines the latest scientific research, philosophy and case studies to examine the perennial human quest to be happy and our seemingly unerring failure to achieve it.

Adam Wishart, a writer and television director, is shortlisted for One in Three, the story of his father's fight against cancer and his attempts to understand some of the most pressing questions raised by the disease.

The shortlist was picked by a team of judges headed by the Open University scientist and leader of the doomed Beagle 2 Mars probe, Colin Pillinger. The winner will be announced on May 15.

The six contenders

Homo Britannicus (Penguin Allen Lane)

Chris Stringer, professor at the Natural History Museum and one of Britain's foremost experts on human origins.

In Search of Memory (WW Norton )

Eric R Kandel, Kavli professor at Columbia University, New York. He received the Nobel prize in physiology or medicine in 2000.

Lonesome George (Macmillan)

Henry Nicholls, writer for Nature and Science. Has a PhD in evolutionary ecology.

One in Three (Profile Books)

Adam Wishart, writer and television director.

Stumbling on Happiness (Harper Press)

Daniel Gilbert, professor of psychology at Harvard University.

The Rough Guide to Climate Change (Rough Guides)

Robert Henson, writer and editor at the National Centre for Atmospheric Research (NCAR).